It is known that antimony-containing metal oxide catalysts, more specifically catalysts comprising the oxides of antimony and at least one metal selected from iron, cobalt, nickel, tin, uranium, chromium, copper, manganese, titanium and cerium are useful in production of aldehydes and acids through the oxidation of organic compounds, in production of dienes, unsaturated aldehydes and unsaturated acids through the oxidative dehydrogenation, and in production of nitriles through ammoxidation. For example, Japanese Patent Publication No. 19111/63 and U.S. Pat. No. 4,377,500 discloses a catalyst comprising the oxides of antimony and iron, cobalt or nickel as a catalyst useful in production of acrylonitrile through ammoxidation of propylene; U.S. Pat. No. 3,152,170 discloses a catalyst comprising the oxides of antimony and tin; U.S. Pat. No. 3,308,151 discloses a catalyst comprising the oxides of antimony and uranium; and U.S. Pat. No. 3,200,081 discloses a catalyst comprising the oxides of antimony and manganese or copper.
Attempts to improve the above catalysts by adding other components have been made. For example, catalyst compositions prepared by adding the oxide of at least one element selected from vanadium, molybdenum and tungsten, and tellurium to each of the oxides of antimony and iron, the oxides of antimony and tin, and the oxides of antimony and uranium are proposed in Japanese Patent Publication Nos. 40958/72 and 19764/72, and U.S. Pat. No. 3,668,147 as multiple acceleration antimony polyvalent metal oxide catalysts.
These antimony-containing metal oxide catalysts, however, have disadvantages in that catalyst production reproducibility is poor, a catalyst having good strength is difficult to obtain, and efficiency in the catalyst production is low. With regard to improvements in the method of preparation thereof, several proposals have been made, as described in, for example, Japanese Patent Publication Nos. 3456/71 and 3457/71, and U.S. Pat. Nos. 3,341,471, 3,657,155 and 3,686,138.
However, various problems in these methods need to be overcome in that catalyst activity and physical properties are both unsatisfactory, or in reproducibility. Furthermore, those catalysts are unsatisfactory in respect of the yield of the desired product.
As a method for preparing a tellurium-containing stable solution, U.S. Pat. No. 4,374,758 discloses a method in which metallic tellurium is reacted with hydrogen peroxide using, as a reaction accelerating agent, the oxide, oxyacid or oxyacid salt of at least one metal selected from the group consisting of vanadium, molybdenum and tungsten. Moreover, a method for preparing catalysts using the above tellurium-containing stable solution is disclosed therein. In accordance with this method, a metal oxide composition containing as essential components antimony and at least one element selected from the group consisting of iron, cobalt, nickel, manganese, uranium, tin and copper is calcined at a temperature of about 500.degree. to 1,000.degree. C., the calcined oxide composition thus obtained is then impregnated with a tellurium-containing solution as described above, dried and again calcined at a temperature of about 400.degree. to 850.degree. C. to obtain the desired antimony and tellurium-containing metal oxide catalyst. Although this method is a good method for preparation of catalysts having high activity and good physical properties, the process is complicated. Thus, a more convenient method is desired for industrial use.
Catalysts containing antimony and tellurium have been produced by the above known antimony-containing metal oxide catalyst preparation methods. In accordance with these methods, however, an antimony-containing metal oxide catalyst with both satisfactory activity and physical properties is difficult to produce with good reproducibility. Moreover, as a result of the tellurium component, the problem, particularly with physical properties is more extended. That is, the catalyst particle density and the catalyst strength are decreased, and moreover, the reproducibility is reduced by an increase in viscosity particularly at the time of pH adjustment during the process of preparation of the catalyst.
Particularly, when a tellurium-containing stable solution prepared by reacting metallic tellurium and hydrogen peroxide using, as a reaction accelerating agent, the oxide, oxyacid or oxyacid salt of at least one metal selected from the group consisting of vanadium, molybdenum and tungsten as described in U.S. Pat. No. 4,374,758 is merely employed as the starting material for the tellurium component in slurry preparation (mixing and pH adjustment) in the methods as described in U.S. Pat. Nos. 3,657,155 and 3,686,138, etc. the above problem tends to be enhanced.
As described above, an antimony and tellurium-containing metal oxide catalyst with both excellent activity and physical properties is difficult to produce conveniently and with good reproducibility by conventional techniques.